Path: utzoo!telecom-request Date: Sun, 19 May 1991 16:20:51 GMT From: "Michael H. Riddle" Newsgroups: comp.dcom.telecom Subject: Re: Cellular Phone Use in Aircraft Message-ID: Organization: University of Nebraska - Lincoln Sender: Telecom@eecs.nwu.edu Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 377, Message 8 of 9 Lines: 73 In ivgate!Jack.Winslade@uunet.uu.net (Jack Winslade) writes: [Most of Jack's comments about HF and Loran-C deleted. Anyone whose idea of a vacation spot is Cape May....] > Now (no grin here) for those of you who happen to live very close to a > Loran-C transmitting station, this case of no interference does not > hold true the other way around. These transmitters pump out RF pulses > in the megawatt range and they have been known to bleed into telephone > lines (sounds like an old mechanical teletype running in the > background) make one heck of a racket in AM and (sometimes) FM radios, > and even cause black and white horizontal 'strobe light' bars on > television pictures. > [Moderator's Note: Have you ever traveled through the rural area in > northern Wisconsin where the ELF (extremely low frequency) > transmitters are located? They send/receive radio transmissions to > submarines. The antennas are strung up and down the highway on > telephone poles! The frequencies which can travel through the earth > and under water are sort of special; they make it possible for a > submarine to receive radio signals without having to expose at least a > little of itself above water; an important feature when used in a spy > operation for military intelligence ... PAT Well, this is getting off the telecom topic a bit, but when I was still in the Air Force I had the job of VLF Systems Integration Manager, and additionally flew as a Communications Control Officer on the SAC Airborne Command Post ("Looking Glass"). We had VLF transmit capability, but our antenna wasn't a mile long. We always had at least 27,000 feet (five miles, more or less) of wire on the reel at takeoff. If we had to extend to transmit, the actual length was frequency dependent but was measured in miles, not feet, for lay purposes. We were using 30-60 kHz. The ELF is down in the 3 - 30 kHZ range, so I suspect the Wisconsin site antennas are bigger than merely one mile and/or are loaded substantially. With sufficient loading, and long ground-plane radials, the actual "in the air" portion of some VLF ground transmitters doesn't have to be more than 2000 feet or so. It all depends on how you design it to meet whatever goals you are addressing. (Historic interlude. If I remember correctly, Marconi's original station on Cape Cod was a VLF installation.) Incidentally, we never extended our VLF antenna over land during peacetime, which is to say we always practiced over water. The SAC airborne used the transverse electric component, so we basically dragged the antenna "straight" behind us. (Obviously, there was a droop.) Some other airborne VLF transmitters would fly in predetermined circles to get a "straight" drop and maximize the transverse magnetic component. Pat's comments about "spy" operation aren't quite on point. Equally important is the invisibility (and hence invulnerability) of the SSBN force (sub-launched ballistic missiles). Finally, in regards to the part of the thread about environmental impact and Jack's comments about receving Loran in TV's, radios and maybe teeth fillings, there was a great deal of opposition to the Wisconsin site because of anticipated interence and unknown long-term effects to low level low frequency radiation. Recent EPA reports, while not yet admitting cause and effect, reinforce the need for concern and study even with power lines. As I remember, the Wisconsin site was scaled back after the protests. I haven't heard what, if any, day-to-day interference they have actually observed. <<<< insert standard disclaimer here >>>> riddle@hoss.unl.edu | Nebraska Inns of Court ivgate!inns!postmaster@uunet.uu.net | +1 402 593 1192 Sysop of 1:285/27@Fidonet | 3/12/24/9600/8N1/V.32/V.42bis